| 摘要 |
PURPOSE: To cool the fuel rods of a fuel assembly in an improved state by arranging a sleeve formed of a sheet around a fuel rod bundle between a pair of spacing pieces on the top of the fuel assembly. CONSTITUTION: A sleeve 10 is sized so that the sleeve 10 can be inserted into an auxiliary assembly channel shown in the figure in an auxiliary assembly 7 between spacing pieces 8 and 9. The sleeve is designed in such a way that, when cooling water is brought to the top of a fuel box, namely, a fuel assembly 7 through the assembly 7 and forms water films on the wall section 6 and fuel rods 1 of the assembly 7, the cooling water flowing down along the wall section 6 of the assembly 7 can come into contact with the sleeve 10. Therefore, the fuel rods of the assembly 7 can be cooled in an improved state, because the sleeve 10 forms a projecting section along the wall section 6 of the assembly 7, scrapes down the cooling water from the wall section 6, and projects the scraped-down water toward the fuel rods in the assembly 7.
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